Over time the fluid carried within a pipe tends to coat the inner walls of the pipe. This coating reduces the cross-sectional area of the interior of the pipe, and reduces the fluid flow. The problem is particularly acute in fired heaters used in oil refineries which cause the crude oil to be heated for the purpose of fractionating the oil into its various components. This process results in impurities attaching to the inside of pipes used in such fired heaters.
A standard method of cleaning pipelines and piping within fired heaters in the oil and gas industry is to drive a pipeline pig through the pipe using fluid pressure. Friction between the exterior of the pipeline pig and the interior surface of the pipe cleans and removes buildup from the pipe.
A typical problem with most pipe pigs is that they are unidirectional, i.e. they are suited for travel in only one direction. As a result, it is not possible to run the pipeline pig back and forth through a limited length of pipe for extra cleaning; the entire pipe must therefore be recleaned. A few pipe pigs are spherical, and therefore suited for travel in any direction, but as a result of their shape have very little surface area to frictionally engage the interior surface of the pipe.
A further problem common to most pipeline pigs is that they do not navigate about bends and corners very well, and the potential for entrapping a pipeline pig within the pipe is quite high.
A still further problem common to most pipeline pigs is that where outwardly directed studs are required to provide the abrasion necessary to clean the inside of a pipeline or piping within a fired heater, there is stress between the pipeline pig and the studs. In time, the stress may cause damage to the pipeline pig, possibly causing tears on the surface of the pipeline pig, adjacent to the outwardly protruding studs. In more extreme cases, the stud may be stripped from the surface of the pipeline pig and lost.
For the foregoing reasons, there is a need for a pipeline pig that can be operated in either direction, that is rugged and durable, having an improved connection between the pipeline pig and any supported studs, and that is suitable for navigating around corners and bends in pipelines.